Most methods for historical document analysis requires a clean or uniform image \(\textbf {x}_{u}\)  as input to extract the text edges or contours.
Therefore, recovering the clean image \(\textbf {x}_{u}\)  given the degraded image \(\textbf {x}\)  is a classical document enhancement problem.
When the uniform \(\textbf {x}_{u}\)  is available, document binarization is quite simple, which can be computed by a global threshold, such as Otsu [1]}.
